When probation is offered to someone it comes with conditions. If it is a condition that you don't live with your gf, that's it for whatever reason your probation officer decides.
You may not be able to live with your gf but that's better than being in a cell-which you will find yourself in if you break an order of your probation like living with your gf and trying to get away with it.
How old is she does she live next to something that is part of your probation rules such as a liquor store or whatever. How old are you? Mayb you are under age and must be with parents or legal guardian. Or maybe she had a felony arrest before